PREVALENCE AND INTENSITY OF BESNOITIA TARANDI IN CARIBOU (RANGIFER TARANDUS) ASSOCIATED RISK FACTORS AND COMPARISONS BETWEEN HERDS Julie Ducrocq, 1 Stéphane Lair, 1 Guy Beauchamp, 1 and Susan Kutz 2 1 Centre québécois sur la santé des animaux sauvages / Canadian Cooperative Wildlife Health Centre. Faculté de médecine vétérinaire, Université de Montréal, St. Hyacinthe, Québec, Canada. 2 Faculty of veterinary medicine, University of Calgary, Calgary, Alberta, Canada. METHODOLOGY In cooperation with the CircumArctic Rangifer Monitoring and Assessment Network, skin sections covering the metatarsal bone were obtained from 1036 caribou between September 2007 and 2009; The prevalence of B. tarandi cysts was determined by histological analysis and intensity of infection was calculated as the number of cysts per mm2 (Fig. 2); Intensity of infection was calculated for each positive animal as the number of cysts per mm 2 (Fig. 2); DISCUSSION DIFFERENCES BETWEEN HERDS B. tarandi is commonly encountered in North American caribou. However, prevalence and intensities of infection vary amongst herds; Prevalence and intensities of infection were higher in caribou from the Leaf River herd then from the other herds. This suggests that these animals are either more exposed to B. tarandi or less resistant to this parasitic infection; B. tarandi was not detected in Greenlandic herds which suggests that it is either absent or below our detection threshold. DIFFERENCES BETWEEN SEASONS The increase in the apparent prevalence following the summer months supports the suspected role of arthropods in the transmission of B. tarandi; DIFFERENCES BETWEEN GENDER Stress and energy expenses associated with male breeding, as well as behaviour, land use and immunomodulating effects of testosterone, might account for the apparent increase of susceptibility of males. POTENTIAL IMPACTS OF B. TARANDI ON CARIBOU POPULATION DYNAMICS The impact of this parasite on the dynamic of the caribou population is unknown, however: Pathology results from animals from the Leaf herd suggest that infection by this parasite can significantly impact on the health of caribou and therefore modulate the survival of some individuals; The frequent occurrence and severity of inflammatory changes in the testes associated with B. tarandi cysts, suggests that this parasite might affect fertility of affected males, as documented with other Besnoitia sp. These preliminary findings show that the relationship between this parasite, its host and the ever changing Arctic environment is worth further investigation. BESNOITIA TARANDI IN CARIBOU (RANGIFER TARANDUS) Is a parasite for which caribou is the intermediate host; Transmission cycle is believed to be a two-host life cycle; carnivores and biting arthropods are thought to be the definitive hosts and the vectors respectively; Lesions are found mainly in the skin and the subcutaneous tissues and manifest themselves as a progressive thickening, hair loss and ulceration, primarily localized on the limbs and on the head; Parasitic cysts (0.5-1 mm in diameter) can be visually observed on the sclera and in affected tissues (Fig. 1A, 1B, 1C); Parasitic cysts are sometimes surrounded by an inflammatory reaction which is especially marked around degenerated cysts (Fig. 1D). RESULTS: RISK FACTORS There was no evidence of B. tarandi cysts in any of the tissues submitted from either of the Greenlandic herds (n=96 females) ; Risk factors associated with B. tarandi infection were geographical locations, gender, age class and season: The odds of infection with B. tarandi were : 64% higher in NA eastern herds (n=718) compared to NA western herds (n=222) (p<0.0001); 78% higher in adult (n=783) compared to calves (n=188) (p<0.0001); 77% higher in yearlings (n=47) compared to calves (n=188) (p<0.0001); 94% higher in fall-winter (n=687) compared to spring-summer (n=345) season (p<0.0001); 33% higher in males (n=335) compared to females (n=658) (p=0.0004). B. tarandi intensity of infection was: 174% higher in NA eastern herds compared to NA western herds (p<0.0001); 48% higher in fall-winter compared to spring-summer season (p=0.0246). RESULTS: COMPARISONS BETWEEN HERDS For adult males sampled in fall (Fig. 3A and B) B. tarandi prevalence and intensity of infection were higher in Leaf River herd compared to Bathurst, Bluenose West and Porcupine (all p values <0.008); For adult females sampled in fall (Fig. 4A and B) B. tarandi prevalence was similar between Leaf River, Bathurst and George River herds (all p values >0.02); B. tarandi intensity of infection was higher for Leaf River herd compared to Bathurst and George River herds (all p values <0.02); For adult females sampled in summer B. tarandi prevalence and intensity of infection were similar between Leaf River (n=50) and George River (n=54) herds (p values>0.05). ACKNOWLEDGEMENT OF CARMA NETWORK COLLABORATORS Joëlle Taillon and Steeve Côté (Université Laval, Québec); Vincent Brodeur, Stéphane Rivard, Lyna Lambert, Andrée-Anne Tremblay and Denis Vandal (Ministère des Ressources naturelles et de la Faune, Québec); Manon Simard, Peter May, Sandy Suppa and Bill Doidge (Nunavik Research Center, Kuujjuak); Brett Elkin, Bruno Croft, Jan Adamczewski, Marsha Branigan, Alasdair Veitch, Richard Popko, Jennifer Bailey, Judy Williams, Fred Manderville, Allicia Kelly, Ernie Campbell, J.P. Rabesca, Lawrence Catholique (Government of the Northwest Territories); Christine Cuyler and her people from the Greenland Institute of Natural Resources. Mitch Campbell from the Nunavut Government and Jane Harms from the University of Saskatchewan; Dorothy Cooley and Martin Kienzler from the Government of Yukon; Pat Curry, Nathan DeBruyn, Dean Brown, Ryan Brook from the University of Calgary; We also would like to acknowledge the following hunters for their participation in community hunter-harvest caribou sampling: Merry Jonas, Henry and Charlie Tobac, Wilbert Kochan, Jared Lafferty, Alvin Orlias, George Oudzi, Angus Shae and Sharon Pierrot from the Northwest Territories and Danis Ohaituk, Tommy Elijassiapik, Aliva Epoo, Epoo Kusudluak, Johnny Naluktuk, Johnny Bobby, Juani Elijassiapik and Thomas Baron from Nunavik. Figure 1. Macroscopic lesions observed in affected caribou (A-conjunctiva; B- periosteum; C- scrotum) and granulomatous inflammatory reaction around a cyst. (D) C BD A Figure 3: Prevalence (A) and intensity (B) of B. tarandi in adult males harvested in fall.Figure 4: Prevalence (A) and intensity (B) of B. tarandi in adult females harvested in fall. Figure 2. Delimitation of the superficial dermis (extending from the external surface of the skin to the base of the hair follicles and adnexal structures) with UTHSCA ImageTool. Multivariate logistic regression models were used to evaluate the association between B. tarandi prevalence and intensity of infection and the following risk factors: Geographical location of herds, gender (males and females), age class (adults, yearling and calves) and season of sampling; The following variables were regrouped: Bluenose West, Bathurst, Southampton and Porcupine as the North American (NA) western herds; George River and Leaf River herds as the NA eastern herds; Akia-Maniitsoq and Kangerlussuaq-Sisimiut herds as the Greelandic herds; Spring/summer and fall/winter seasons. B. tarandi status was logit transformed; Intensity was analyzed using a negative binomial model; The natural logarithm of the sampled area was used as an offset. Comparison of prevalence and density of infection between herds Analysis was performed according to gender, age class and season of sampling; Statistical significance was established with a two-sample t-test for means or for proportion; For the all variable comparisons, α level was adjusted downward with the sequential Bonferroni adjustment in order to maintain the overall probability of a type I error at Bathurst (n=28) Bluenose W. (n=25) Leaf River (n=44) A Porcupine (n=13) 8% 44% 39% 77% Bathurst (n=25) Leaf River (n=85) A 32% 38% 57% George River (n=29) Image source: Central Image Gallery of CARMA network J. TaillonC.CuylerL.WitterA.Bali Mild outliers ( ) B B Mild ( ) and extreme ( ) outliers